The functional response types and parameters of 3rd and 4th instar larvae, and adult females and males of a coccinellid predator, Adalia fasciatopunctata revelierei (Mulsant) (Col.: Coccinellidae), were evaluated at five different densities of Callaphis juglandis (Goeze) (Hemiptera: Aphididae) in order to understand their role for the aphid's biological control. Experiments were carried out in petri dishes at 25 +/- 1 degrees C, 60 +/- 10% r. h. and 16L:8D photoperiod in a controlled temperature room. All tested stages exhibited a Type II response determined by a logistic regression model. The attack rate (alpha) and handling time (T(h)) coefficients of a Type II response were estimated by fitting a "random-predator" equation to the data. Although the estimates of alpha for all stages of A. fasciatopunctata revelierei tested were similar, the longest T(h) was obtained for 3rd instar larva because of the lower consumption rate at densities above 40 prey/day. Results indicated that the adult female has the highest predation of C. juglandis followed by 4th instar larvae, adult males and 3rd instar larvae. However, further field-based studies are needed to draw firm conclusions.